Compressor diagnostic system

ABSTRACT

A diagnostic system and method for a compressor assembly including a compressor and a motor protector includes logic circuitry associated with the motor protector and operable to analyze a status of the motor protector as a function of time and identify a specific fault cause. The diagnostic system also includes a demand signal sensor and a current sensor, wherein the logic circuitry is associated with the sensors to further enable the diagnostic system to determine a specific fault cause.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/990,566 filed on Nov. 21, 2001, which is acontinuation-in-part application of U.S. patent application Ser. No.09/818,271 filed on Mar. 27, 2001 (now U.S. Pat. No. 6,615,594). Thedisclosure of the above application is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a diagnostic system for arefrigeration or air-conditioning system. More particularly, the presentinvention relates to a diagnostic system for a refrigeration orair-conditioning system which uses various operating characteristics andthe compressor's “trip” information to diagnose the problems associatedwith the refrigeration or air-conditioning system.

BACKGROUND AND SUMMARY OF THE INVENTION

[0003] A class of machines exists in the art generally known as scrollmachines which are used for the displacement of various types of fluid.These scroll machines can be configured as an expander, a displacementengine, a pump, a compressor, etc., and the features of the presentinvention are applicable to any of these machines. For purposes ofillustration, however, the disclosed embodiment is in the form of ahermetic refrigerant scroll compressor used within a refrigeration orair conditioning system.

[0004] Scroll compressors are becoming more and more popular for use ascompressors in both refrigeration as well as air conditioningapplications due primarily to their capability for extremely efficientoperation. Generally, these machines incorporate a pair of intermeshedspiral wraps, one of which is caused to orbit relative to the other soas to define one or more moving chambers which progressively decrease insize as they travel from an outer suction port toward a center dischargeport. An electric motor is provided which operates to drive the orbitingscroll member via a suitable drive shaft affixed to the motor rotor. Ina hermetic compressor, the bottom of the hermetic shell normallycontains an oil sump for lubricating and cooling purposes. While thediagnostic system of the present invention will be described inconjunction with a scroll compressor, it is to be understood that thediagnostic system of the present invention can be used with other typesof compressors also.

[0005] Traditionally, when an air conditioning or refrigeration systemis not performing as designed, a technician is called to the site fortrouble shooting the problem. The technician performs a series of checksthat assists in isolating the problem with the system. One of the causesof the system's problem could be the compressor used in the system. Afaulty compressor exhibits some operational patterns that could be usedto detect the fact that the compressor is faulty. Unfortunately, manyother causes for system problems can be attributed to other componentsin the system and these other causes can also affect the performance ofthe compressor and its operational pattern. It is possible to analyzethe system's problems and operational patterns and determine that thecompressor is faulty when in fact the problem lies elsewhere and thecompressor is not the problem. This confusion of causes usually resultsin the replacement of a good compressor. This error in diagnosis iscostly since the compressor is generally the most expensive component inthe system. Further aggravating the problem is that the root cause forthe system's problem has not been solved and the problem recurs in time.Any tool which can help avoid the misdiagnosing of the system's problemas described above would prove both useful and cost effective. Thepresent invention discloses a device that increases the accuracy of theproblem diagnosis for an air conditioning or refrigeration system.

[0006] A large part of the compressors used in air conditioning andrefrigeration systems have built-in protection devices called “internalline break protectors”. These protectors are thermally sensitive deviceswhich are wired in electrical series with the motor. The protectorsreact thermally to the line current drawn by the motor and also othertemperatures within the compressor including but not limited todischarge gas temperature, suction gas temperature or temperature of aparticular component in the compressor. When one of these temperaturesexceeds a designed threshold, the protector will open the electricalconnection to the motor. This shuts down the motor operating thecompressor which in turn shuts down the compressor and prevents it fromoperating in regions that would lead to its failure. After a period oftime, when the temperatures have fallen to safe levels, the protectorautomatically resets itself and the compressor operates again. Thetemperatures that the protector is reacting to are a result of theoperation of the compressor and the entire refrigeration orair-conditioning system. Either the operation of the compressor or theoperation of the entire system can influence the temperatures sensed bythese protectors. The significant aspect of the protection system isthat some categories of faults repeatedly trip the protector with veryshort compressor ON time and other categories of faults trip theprotector less frequently thus providing relatively longer compressor ONtimes. For example, a compressor with seized bearings would trip theprotector within about twenty seconds or less of ON time. On the otherhand, a system that has a very low refrigerant charge will trip theprotector after typically more than ninety minutes of ON time. Ananalysis of the trip frequency, trip reset times and compressor ON timeswill provide valuable clues in identifying the cause of the system'sproblems.

[0007] The present invention provides a device which is based on thisprinciple. The device of the present invention continuously records thestatus of the protector (open or closed) as a function of time and thenit analyzes this status information to determine a faulty situation. Thedevice goes further and isolates the fault to either the compressor orto the rest of the system. Once the fault has been isolated, the devicewill activate a visual indicator (light) and it will also send anelectrical signal to any intelligent device (controller, computer, etc.)advising about the situation. The technician, on arriving at the scene,then has a clear indication that the problem is most likely in thesystem components other than the compressor or the problem is mostlikely in the compressor. He can then focus his further trouble shootingto the identified area. The device thus avoids the previously describedsituation of a confused diagnosis and the potential of mistakenlyreplacing a good compressor.

[0008] In addition to the status of the protector, additionalinformation can be gathered by sensors that monitor other operatingcharacteristics of the refrigeration system such as supply voltage andoutdoor ambient temperature. This additional information can then beused to further diagnose the problems associated with the refrigerationor air-conditioning system.

[0009] Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while indicating the preferred embodiment of the invention,are intended for purposes of illustration only and are not intended tolimit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

[0011]FIG. 1 is a vertical cross section of a hermetic scroll compressorincorporating the unique compressor diagnostic system in accordance withthe present invention;

[0012]FIG. 2 is a schematic representation of the diagnostic system fora single phase motor for the compressor in accordance with the presentinvention;

[0013]FIG. 3 is a schematic representation of a diagnostic system for athree phase motor for the compressor in accordance with anotherembodiment of the present invention;

[0014]FIG. 4 is a flow diagram of the diagnostic system for the singlephase motor for the compressor in accordance with the present invention;

[0015]FIG. 5 is a flow diagram of the diagnostic system for the threephase motor for the compressor in accordance with the present invention;

[0016]FIG. 6 is a flow diagram which is followed when diagnosing acompressor system;

[0017]FIG. 7 is a schematic view of a typical refrigeration systemutilizing the compressor and diagnostic system in accordance with thepresent invention;

[0018]FIG. 8 is a perspective view of a contactor integrated with thediagnostic system's circuitry in accordance with another embodiment ofthe present invention;

[0019]FIG. 9 is a schematic view illustrating the circuitry of thecontactor illustrated in FIG. 8;

[0020]FIG. 10 is a schematic view of a compressor plug which illustratesthe diagnostic system's circuitry in accordance with another embodimentof the present invention;

[0021]FIG. 11 is a flow diagram of a diagnostic system for thecompressor in accordance with another embodiment of the presentinvention;

[0022]FIG. 12 is a chart indicating the possible system faults basedupon ON time before trips;

[0023]FIG. 13 is a graph showing electrical current versus thetemperature of the condenser;

[0024]FIG. 14 is a graph showing percent run time versus outdoor ambienttemperature; and

[0025]FIG. 15 is a schematic illustration of a diagnostic system inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following description of the preferred embodiment(s) ismerely exemplary in nature and is in no way intended to limit theinvention, its application, or uses.

[0027] Referring now to the drawings in which like reference numeralsdesignate like or corresponding parts throughout the several views,there is shown in FIG. 1 a scroll compressor incorporating the uniquecompressor diagnostic system in accordance with the present inventionand which is designated generally by the reference numeral 10. Whilecompressor 10 is being illustrated as a scroll compressor in conjunctionwith a refrigeration or air conditioning system, it is within the scopeof the present invention to utilize other types of compressors in therefrigeration or air conditioning system if desired as well as havingany of the compressor designs being in conjunction with other types ofsystems.

[0028] Scroll compressor 10 comprises a generally cylindrical hermeticshell 12 having welded at the upper end thereof a cap 14 and at thelower end thereof a base 16 having a plurality of mounting feet (notshown) integrally formed therewith. Cap 14 is provided with arefrigerant discharge fitting 18 which may have the usual dischargevalve therein. A transversely extending partition 20 is affixed to shell12 by being welded about is periphery at the same point that cap 14 iswelded to shell 12. A compressor mounting frame 22 is press fit withinshell 12 and it is supported by the end of base 16. Base 16 is slightlysmaller in diameter than shell 12 such that base 16 is received withinshell 12 and welded about its periphery as shown in FIG. 1.

[0029] Major elements of compressor 10 that are affixed to frame 22include a two-piece main bearing housing assembly 24, a lower bearinghousing 26 and a motor stator 28. A drive shaft or crankshaft 30 havingan eccentric crank pin 32 at the upper end thereof is rotatablyjournaled in a bearing 34 secured within main bearing housing assembly24 and a second secured within lower bearing housing 26. Crankshaft 30has at the lower end thereof a relatively large diameter concentric bore38 which communicates with a radially outwardly positioned smallerdiameter bore 40 extending upwardly therefrom to the top of crankshaft30. The lower portion of the interior of shell 12 defines an oil sump 44which is filled with lubricating oil to a level slightly above the lowerend of a rotor, and bore 38 acts as a pump to pump lubricating fluid upcrankshaft 30 and into bore 40 and ultimately to all of the variousportions of compressor 10 which require lubrication.

[0030] Crankshaft 30 is rotatably driven by an electric motor whichincludes stator 28, windings 46 passing therethrough and a rotor 48press fitted into crankshaft 30. An upper counterweight 50 is secured tocrankshaft 30 and a lower counterweight 52 is secured to rotor 48. Atemperature protector 54, of the usual type, is provided in closeproximity to motor windings 46. Temperature protector 54 willde-energize the motor if thermal protector 54 exceeds its normaltemperature range. Temperature protector 54 can be heated by motorwindings 46, suction gas within a suction chamber 56 and/or dischargegas within a discharge chamber 58 which is released into suction chamber56. Both suction chamber 56 and discharge chamber 58 are defined byshell 12, cap 14, base 16 and partition 22 as shown in FIG. 1.

[0031] The upper surface of two-piece main bearing housing assembly 24is provided with a flat thrust bearing surface on which is disposed anorbiting scroll member 60 having the usual spiral vane or wrap 62extending upward from an end plate 64. Projecting downwardly from thelower surface of end plate 64 of orbiting scroll member 60 is acylindrical hub 66 having a journal bearing therein and which isrotatably disposed a drive bushing 68 having an inner bore in whichcrank pin 32 is drivingly disposed. Crank pin 32 has a flat on onesurface which drivingly engages a flat surface formed in a portion ofthe inner bore of drive bushing 68 to provide a radially compliantdriving arrangement, such as shown in Assignee's U.S. Letters Pat. No.4,877,382, the disclosure of which is hereby incorporated herein byreference. An Oldham coupling 70 is also provided positioned betweenorbiting scroll member 60 and two-piece bearing housing assembly 24.Oldham coupling 70 is keyed to orbiting scroll member 60 and to anon-orbiting scroll member 72 to prevent rotational movement of orbitingscroll member 60.

[0032] Non-orbiting scroll member 72 is also provided with a wrap 74extending downwardly from an end plate 76 which is positioned in meshingengagement with wrap 62 of orbiting scroll member 60. Non-orbitingscroll member 72 has a centrally disposed discharge passage 78 whichcommunicates with an upwardly open recess 80 which is in turn incommunication with discharge chamber 58. An annular recess 82 is alsoformed in non-orbiting scroll member 72 within which is disposed afloating seal assembly 84.

[0033] Recesses 80 and 82 and floating seal assembly 84 cooperate todefine axial pressure biasing chambers which receive pressurized fluidbeing compressed by wraps 62 and 74 so as to exert an axial biasingforce on non-orbiting scroll member 72 to thereby urge the tips ofrespective wraps 62 and 74 into sealing engagement with the opposed endsurfaces of end plates 76 and 64, respectively. Floating seal assemblyis preferably of the type described in greater detail in Assignee's U.S.Letters Pat. No. 5,156,639, the disclosure of which is herebyincorporated herein by reference. Non-orbiting scroll member 72 isdesigned to be mounted for limited axial movement with respect totwo-piece main bearing housing assembly 24 in a suitable manner such asdisclosed in the aforementioned U.S. Letters Pat. No. 4,877,382 orAssignee's U.S. Letters Pat. No. 5,102,316, the disclosure of which ishereby incorporated herein by reference.

[0034] Compressor 10 is powered by electricity which is provided to theelectric motor within shell 12 through a molded electric plug 90.

[0035] Referring now to FIGS. 1 through 3, the present invention isdirected to a unique compressor diagnostic system 100. Diagnostic system100 comprises one or more current sensing devices 102 and the associatedlogic circuitry 104. Current sensing devices 102 are mounted in ahousing 106. mounted externally to shell 12. Logic circuitry 104 can bemounted in housing 106 or it can be located in a convenient positionwith respect to compressor 10 as shown in phantom in FIG. 2. Optionally,the sensing device and circuitry can be integrated into a specialcontactor, a special wiring harness or into a molded plug utilized forsome compressor designs.

[0036] Current sensing devices 102 sense the current in the power supplywires powering compressor 10. FIG. 2 illustrates two current sensingdevices 102 in conjunction with a single-phase motor. One of the currentsensing devices 102 is associated with the main windings for thecompressor motor and the other current sensing device 102 is associatedwith the auxiliary windings for the compressor motor. FIG. 3 alsoillustrates two current sensing devices 102 in conjunction with a threephase motor. Each current sensing device 102 is associated with one ofthe phases of the three phase power supply. While FIG. 3 illustrates twocurrent sensing devices sensing current in two phases of the three phasepower supply, it is within the. scope of the present invention toinclude a third current sensor 102 to sense the current in the thirdphase of the three phase power supply as shown in phantom in FIG. 3 ifdesired. These current signals represent an indication of the status ofprotector 54 (open or closed). While current sensing devices 102 sensethe status of protector 54 utilizing the current in the power supplywires, it is also possible to sense the status of protector 54 bysensing the presence or absence of voltage on the motor side ofprotector 54. The inventors of the present invention consider this to bea less desirable but effective approach in some cases because itrequires an additional hermetic feed-through pin extending through shell12. The signals received from current sensing devices 102 are combinedin logic circuitry 104 with the demand signal for compressor 10. Thedemand signal for compressor 10 is acquired by sensing the presence ofsupply voltage or by having a system controller (not shown) supply adiscrete signal representing the demand. The demand signal and thesignal received by logic circuitry 104 are processed by logic circuitry104 to derive the information about the trip frequency of protector 54and the average ON time and OFF time of compressor 10. Logic circuitry104 analyses the combination of current signals, the demand signal andthe derived protector trip frequencies to determine if a fault conditionexists. Logic circuitry also has the unique capability of identifying aspecific cause based on some faults. This information is provided to theservice people using a green LED light 110 and a yellow LED light 112.Green LED light 110 is utilized to indicate that there is currently nofault condition and that the system is functioning normally.

[0037] Yellow LED light 112 is utilized to indicate the presence of afault. When yellow LED light 112 is turned ON, green LED light 110 isturned OFF. Thus, yellow LED light 112 is utilized to visuallycommunicate that there is a fault as well as indicating the type offault that is present. This communication is accomplished by turningyellow LED light 112 ON and then OFF for a specific duration andsequence to indicate both that there is a fault and to identify what thefault is. For example, turning light 112 ON for one second and turningit OFF for nineteen seconds and repeating this sequence every twentyseconds will create the effect of a blinking light that blinks ON onceevery twenty seconds. This sequence corresponds to a type of fault thatis coded as a type 1 fault. If light 112 is blinked ON twice for onesecond during the twenty second window, it is an indication that a faultthat is coded as a type 2 is present. This sequence continues toindicate a type 3, a type 4 and so on with the type of fault beingindicated by the number of blinks of light 112. This scheme of theblinking of light 112 for a specific number of times is employed tovisually communicate to the technician the various types of faultsdetected by logic circuitry 104. While the present invention utilizesblinking light 112 to convey the fault codes, it is within the scope ofthe present invention to utilize a plurality of lights to increase theeffectiveness of conveying a large number of fault codes if desired. Inaddition, other methods of providing the default code, includingproviding a coded voltage output that can be interfaced with otherelectronic devices, can also be employed.

[0038] In addition to visually communicating the specific fault codeusing light 112, logic circuitry 104 also outputs a coded sequence ofelectrical pulses to other intelligent controllers that may exist in thesystem. These coded pulses represent the type of fault that has beendetected by diagnostic system 100. The types of faults which can bedetected by logic circuitry 104 include, but are not limited to:

[0039] 1. Protector has “tripped”.

[0040] 2. The auxiliary winding of a single phase motor has no power oris open or has a faulty run capacitor.

[0041] 3. The main winding of a single phase motor has no power or thatthe winding is open.

[0042] 4. The main circuit breaker has contacts that have welded shut.

[0043] 5. One of the phases in a 3 phase circuit is missing.

[0044] 6. The phase sequence in a 3 phase system is reversed.

[0045] 7. The supply voltage is very low.

[0046] 8. The rotor inside the compressor has seized.

[0047] 9. The protector is tripping due to system high pressure siderefrigeration circuit problems.

[0048] 10. The protector is tripping due to system lower pressure siderefrigeration circuit problems.

[0049] 11. The motor windings are open or the internal line breakprotector is faulty.

[0050] 12. The supply voltage to the compressor is low.

[0051] As a variation to the above, as shown in FIG. 3, diagnosticsystem 100 may only send the status of protector 54 to an intelligentdevice 116. In this option, the parameters of trip frequencies, ON timesand OFF times with the diagnosis information may be generated atintelligent device 116. Intelligent device 116 can be a compressorcontroller associated with compressor 10, it can be a system controllermonitoring a plurality of compressors 10, it can be a remotely locateddevice or it can be any other device which is selected to monitordiagnostic system 100 of one or more compressors.

[0052]FIG. 4 represents a flow diagram for diagnostic system 100 inconjunction with a single phase compressor. The demand signal isprovided to logic circuitry 104 from a device or a contactor 120 (FIGS.2 and 3) along with the current signal from sensing devices 102. Whenthe system is initially powered up, an initializing process is performedat 122 and, if successful, the system, as shown by arrow 124, goes to anormal OFF condition as shown at 126. When sitting at the normal OFFcondition 126, if a demand signal is provided to the system, the systemmoves as shown by arrow 128 to a normal run condition shown at 130. Oncethe demand has been met, the system returns to the normal OFF condition126 as shown by arrow 132.

[0053] While sitting at the normal OFF condition 126, if current in themain winding or current in the auxiliary winding is detected and therehas been no demand signal, the system moves as shown by arrow 134 to ashorted contactor condition 136. While indicating the shortenedcontactor condition 136, if the demand is signaled, the system moves asshown by arrow 138 to the normal run condition 130. The normal runcondition 130 continues until the demand has been satisfied where thesystem moves as shown by arrow 132 back to the normal OFF condition 126which may again move to the shortened contactor condition 136 dependingon whether or not current is sensed in the main or auxiliary windings.

[0054] While operating in the normal run condition 130, one of threepaths other than returning to the normal OFF condition 126 can befollowed. First, if the system senses demand and main winding currentbut does not sense auxiliary winding current, the system moves as shownby arrow 140 to an open auxiliary circuit condition 142. From here, thesystem moves to a protector tripped condition 144 as shown by arrow 146when both a main winding current and an auxiliary winding current arenot sensed. Second, if the system senses demand and auxiliary windingcurrent but does not sense main winding current, the system moves asshown by arrow 148 to an open main circuit condition 150. From here, thesystem moves to the protector tripped condition 144 as shown by arrow152 when both a main winding current and an auxiliary winding currentare not sensed. Third, if the system senses demand and does not senseauxiliary winding current and main winding current, the system moves asshown by arrow 154 to the protector tripped condition 144.

[0055] While operating in the protector tripped condition 144, one offour paths can be followed. First, if main winding current or auxiliarywinding current is sensed and the demand is satisfied, the system movesas shown by arrow 160 to the normal run condition 130. Second, with theprotector tripped, and the moving window average of the ON time of thesystem has been less than twelve seconds, the system moves as shown byarrow 162 to a multiple short run condition 164. From the multiple shortrun condition, the system moves back to the protector tripped condition144 as shown by arrow 166. Third, with the protector tripped, and themoving window average of the ON time of the system has been greater thanfifteen minutes, the system moves as shown by arrow 168 to a multiplelong run condition 170. The system moves back to the protector trippedcondition 144 as shown by arrow 172. Fourth, with the protector tripped,if the tripped time exceeds four hours, the system moves as shown byarrow 174 to a power loss or protector defective condition 176. If,while the system is in the power loss or protector defective condition176 and main winding current or auxiliary winding current is sensed, thesystem moves back to the protector tripped condition 144 as shown byarrow 178.

[0056] When the system moves to the various positions shown in FIG. 4,the blinking of light 112 is dictated by the fault condition sensed. Inthe preferred embodiment, if a protector tripped condition is sensed at154 because demand is present but current is missing, light 112 blinksonce. If compressor 10 is seized or there is a low supply voltageproblem such as indicated by arrow 162 because the average ON timeduring the last five trips was less than twelve seconds, light 112blinks twice. If the motor windings are open, the protector is faulty orthe contactor is faulty as indicated by arrow 174 because the OFF timeis greater than four hours, light 112 blinks three times. If theauxiliary windings are open or there is a faulty run capacitor asindicated by arrow 140, light 112 blinks four times. If the main windingis open as indicated by arrow 148, light 112 blinks five times. If thecontactor is welded as indicated by arrow 134 because current is sensedbut there is no demand, light 112 blinks six times. Finally, if thereare repeated protector trips due to other system problems as indicatedby arrow 168 because the average ON time during the last five trips wasless than fifteen minutes, light 112 blinks seven times.

[0057]FIG. 5 represents a flow diagram for diagnostic system 100 inconjunction with a three phase compressor. The demand signal is providedto logic circuitry 104 from contactor 120 (FIGS. 2 and 3) along with thecurrent signal from sensing devices 102. When the system is initiallypowered up, an initializing process is performed at 122 and, ifsuccessful, the system, as shown by arrow 124, goes to a normal OFFcondition as shown at 126. When sitting at the normal OFF condition 126,if a demand signal is provided to the system, the system moves as shownby arrow 128 to a normal run condition shown at 130. Once the demand hasbeen met, the system returns to the normal OFF condition 126 as shown byarrow 132.

[0058] While sitting at the normal OFF condition 126, if current in oneof the three phases or current in a second of the three phases isdetected and there has been no demand signal the system moves as shownby arrow 234 to a shorted contactor condition 136. While indicating theshortened contactor condition 136, if the demand is signaled, the systemmoves as shown by arrow 238 to the normal run condition 130. The normalrun condition 130 continues until the demand has been satisfied wherethe system moves as shown by arrow 132 back to the normal OFF condition126 which may again move to the shortened contactor condition 136depending on whether or not current is sensed in the main or auxiliarywindings.

[0059] While operating in the normal run condition 130, one of threepaths other than returning to the normal OFF condition 126 can befollowed. First, if the system senses demand and eleven milliseconds isless than the zero crossing time difference between the first and secondphases of the three phase power supply or this time difference is lessthan fourteen milliseconds, the system moves as shown by arrow 240 to aphase sequence reversed condition 242. From here, the system moves to aprotector tripped condition 144 as shown by arrow 246 when both a firstphase current or a second phase current is not sensed. Second, if thesystem senses demand and sixteen milliseconds is less than the zerocrossing time difference between the first and second phases or thistime difference is less than twenty-one milliseconds, the system movesas shown by arrow 248 to a phase missing condition 250. From here, thesystem moves to the protector tripped condition 144 as shown by arrow252 when both a first phase current and a second phase current are notsensed. Third, if the system senses demand and does not sense firstphase current and second phase current, the system moves as shown byarrow 254 to the protector tripped condition 144.

[0060] While operating in the protector tripped condition 144, one offour paths can be followed. First, if first phase current or secondphase current is sensed and the demand is satisfied, the system moves asshown by arrow 260 to the normal run condition 130. Second, with theprotector tripped, and the moving window average of the ON time of thesystem has been less than twelve seconds, the system moves as shown byarrow 162 to a multiple short run condition 164. From the multiple shortrun condition, the system moves back to the protector tripped condition144 as shown by arrow 166. Third, with the protector tripped, and themoving window average of the ON time of the system has been greater thanfifteen minutes, the system moves as shown by arrow 168 to a multiplelong run condition 170. The system moves back to the protector trippedcondition 144 as shown by arrow 172. Fourth, with the protector tripped,if the tripped time exceeds four hours, the system moves as shown byarrow 174 to a power loss or protector defective condition 176. If,while the system is in the power loss or protector defective condition176 and first phase current or second phase current is sensed, thesystem moves back to the protector tripped condition 144 as shown byarrow 278.

[0061] When the system moves to the various positions shown in FIG. 5,the blinking of light 112 is dictated by the fault condition sensed. Inthe preferred embodiment, if a protector tripped condition is sensed at254 because demand is present but current is missing, light 112 blinksonce. If compressor 10 is seized or there is a low supply voltageproblem such as indicated by arrow 162 because the average ON timeduring the last five trips was less than twelve seconds, light 112blinks twice. If the motor windings are open, the protector is faulty orthe contactor is faulty as indicated by arrow 174 because the OFF timeis greater than four hours, light 112 blinks three times. If thecontactor is welded as indicated by arrow 234 because current is sensedbut there is no demand, light 112 blinks four times. If there arerepeated protector trips due to other system problems as indicated byarrow 168 because the average ON time during the last five trips wasless than fifteen minutes, light 112 blinks five times. If the powersupply phases are reversed as indicated by arrow 240 because the zerocrossing time difference is between eleven and fourteen milliseconds,light 112 blinks six times. Finally, if there is a phase missing in thethree phase power supply as indicated by arrow 248 because the zerocrossing time difference is between sixteen and twenty-one milliseconds,light 112 blinks seven times.

[0062] While the above technique has been described as monitoring themoving window averages for compressor 10, it is within the scope of thepresent invention to have logic circuitry 104 utilize a real time or theinstantaneous conditions for compressor 10. For instance, in looking atarrows 162 or 168, rather than looking at the moving window average,logic circuitry 104 could look at the previous run time for compressor10.

[0063]FIG. 6 represents a flow diagram which is followed when diagnosinga system problem. At step 300, the technician determines if there is aproblem by checking the LEDs at step 302. If green LED 110 is lit, theindication at 304 is that compressor 10 is functioning normally and theproblem is with other components. If yellow LED light 112 is blinking,the technician counts the number of blinks at 306. Based upon the numberof blinks of light 112 the determination of the failure type is made at308. The fault is corrected and the system is recycled and started at310. The system returns to step 300 which again will indicate any faultswith compressor 10.

[0064] Thus, diagnostic system 100 provides the technician who arrivesat the scene with a clear indication of most likely where the problemwith the system is present. The technician can then direct his attentionto the most likely cause of the problem and possibly avoid thereplacement of a good compressor.

[0065]FIG. 7 illustrates a typical refrigeration system 320.Refrigeration system 320 includes compressor 10 in communication with acondensor 322 which is in communication with an expansion device 324which is in communication with an evaporator 326 which is incommunication with compressor 10. Refrigerant tubing 328 connects thevarious components as shown in FIG. 7.

[0066] Referring now to FIG. 8, a contactor 120 is illustrated whichincorporates diagnostic system 100 in the form of current sensors 102,logic circuitry 104, green LED light 110 and yellow light 112. Contactor120 is designed to receive information from various system controls suchas a system thermostat 350 (FIGS. 2 and 3), a group of system safeties352 (FIGS. 2 and 3) and/or other sensors incorporated into the systemand based upon three inputs provide power to compressor 10.

[0067] Contactor 120 includes a set of power-in connectors 354, a set ofpower-out connectors 356, a set of contactor coil connectors 358, light110 and light 112. The internal schematic for contactor 120 is shown inFIG. 9. A power supply 360 receives power from connectors 354, convertsthe input power as needed and then supplies the required power to inputcircuitry 362, processing circuitry 364 and output circuitry 366, whichcollectively form logic circuitry 104.

[0068] Input circuitry 362 receives the input from current sensors 102and the demand signal in order to diagnose the health of compressor 10.The information received by input circuitry 362 is directed toprocessing circuitry 364 which analyses the information provided andthen provides information to output circuitry 366 to operate compressor10 and/or activate LED lights 110 and 112. The incorporation of logiccircuitry 104 into contactor 120 simplifies the system due to the factthat both the line power and the demand signal are already provided tocontactor 120. The function and operation of diagnostic system 100incorporated into contactor 120 is the same as described above forhousing 106.

[0069] Referring now to FIG. 10, molded plug 90 is illustratedincorporating diagnostic system 100 in the form of current sensors 102,logic circuitry 104, light 110 and light 112. In some applications,incorporation of diagnostic system 100 into molded plug 90 offers somedistinct advantages. When diagnostic system 100 is incorporated intomolded plug 90, power is provided through connectors 354 and must alsobe provided to diagnostic system from the input power or it can beprovided separately through connector 370. In addition, the demandsignal must also be provided to plug 90 and this can be done throughconnectors 372. The function and operation of diagnostic system 100incorporated into molded plug 90 is the same as described above forhousing 106. Communication from plug 90 is accomplished throughconnection 374.

[0070]FIGS. 4 and 5 illustrate flow diagrams for diagnostic system 100.While operating in the protector tripped condition 144, different pathsare followed depending upon the moving window average of the ON time orthe previous cycle ON time. These various paths help to determine whattype of fault is present.

[0071] This concept can be expanded by making additional assumptionsbased upon the compressor ON time between overload trips. The compressorON time duration prior to the overload trip can be expanded to be usefulin diagnosing whether the fault is likely located on the high-side(condenser) or on the low-side (evaporator) of the refrigeration or airconditioning system. This added information would help the technicianspeed up his search for the fault. FIG. 11 illustrates the flow diagramfor a diagnostic system 100. While FIG. 11 illustrates a diagnosticsystem for a single phase motor, the diagnostic system illustrated inFIG. 11 and described below can be utilized with a three phase motor, ifdesired.

[0072] Using this approach, there are four major system faults as shownin FIG. 12 that can be identified based on the ON time and/or OFF time.First, a “locked rotor” (LR Trip) condition typically results from acompressor mechanical lock-out or a hard start problem. This results inthe shortest trip time usually within twenty seconds or less. This isillustrated in FIG. 11 by arrow 162′ which leads to a locked rotorcondition 164: from the locked rotor condition 164; the system movesback to the protector tripped condition 144 as shown by arrow 166′.Second, a “short cycling” condition is typically due to cut-in andcut-out of either the high-side or the low-side safety pressureswitches. Both the ON time and OFF time during short cycling aretypically in the order of two minutes or less. This is illustrated inFIG. 11 by arrow 162″ which leads to a short cycling run condition 164″.From the short cycling run condition 164″, the system moves back to theprotector tripped condition 144 as shown by arrow 166″. Third, a “normaloverload trip” (protector trip) condition is the one expected to occurmost often imposing a max-load condition on the compressor due to systemfaults such as a blocked or failed condenser fan. The ON time betweentrips can be anywhere from four to ninety minutes depending on theseverity of the faults. This is illustrated in FIG. 11 by arrow 168′which leads to a normal overload trip condition 170′. From the normaloverload trip condition 170′, the system moves back to the protectortripped condition 144 as shown by arrow 172′. As shown in FIG. 12, thenormal overload trip can be broken down into two separate areas of thetemperature if condenser 322 (Tc) is known. Fourth, a “high run time”fault condition results in very long run times typically greater thanninety minutes. A normal fifty per-cent run-time thermostat cyclingbased on a rate of three cycles per hour would produce an ON time of tenminutes. Thus, running more than ninety minutes is typically a fault.This is illustrated in FIG. 11 by arrow 174′ which leads to a loss ofcharge fault 176′. From the loss of charge fault 176′, the system movesback to the protector tripped condition 144 as shown by arrow 178′.Diagnostic system 100′ can replace diagnostic system 100 shown in FIGS.4 and 5 or diagnostic system 101′ can run concurrently with these othertwo diagnostic systems.

[0073] Additional information can be obtained using additional sensors.By adding key sensors, the diagnostic systems described above can extendinto a major capability that can clearly distinguish between acompressor fault and a system fault on any set or conditions.

[0074] Specifically, for a given voltage and power supply type, therunning current for compressor 10 is mainly a prescribed function of itsdischarge pressure and its suction pressure as represented by typicalpublished performance tables or equations. Typically, for most scrollcompressors, the compressor current varies mainly with the dischargepressure and it is fairly insensitive to suction pressure. When amechanical failure occurs inside scroll compressors, its current drawwill increase significantly at the same discharge pressure. Therefore,by sensing current with current sensing devices 102 and by sensingdischarge pressure using a sensor 330 as shown in FIG. 7, most faultsinside compressor 10 can be detected. For a given power supply, a changein voltage can affect its current. However, these voltage changes areusually intermittent and not permanent, while a fault is typicallypermanent and irreversible. This difference can be distinguished bydetecting the current with current sensing devices 102 and by detectingthe discharge pressure with sensor 330 for several repetitive cycles.

[0075] Typically, discharge pressure sensor 330 is a fairly expensivecomponent, especially for residential system implementation. A low-costalternative is to use a temperature sensor CR thermistor 332 as shown inFIG. 7 mounted at the mid-point of condenser 322 on one of the tubehairpin or return bends. This temperature sensing is fairly well knownas it is used with demand-type defrost control for residential heatpumps. FIG. 13 illustrates a typical relationship between compressorcurrent and condensing temperature. A generic equation or table for thisrelationship can be pre-programmed into diagnostic systems 100 or 100′.Then by measuring two or three coordinate points during the initialtwenty-four hours of operation after the first clean installation, thecurve can then be derived and calibrated to the system for use as ano-fault reference.

[0076] In addition to current sensing devices 102, pressure sensor 330or temperature sensor 332, an outdoor ambient temperature sensor 334 asshown in FIGS. 2 and 3 may be added. The addition of sensor 334 ismainly for detecting compressor faults by leveraging the data fromsensors 102 and 330 or 332 with the data from sensor 334. Since bothtemperature sensor 332 and temperature sensor 334 are typically usedwith demand-type defrost controls in residential heat pumps, thisconcept is fairly attractive because the technicians are alreadyfamiliar with these sensors and the added cost is only incremental.

[0077] The combination of condensing temperature and condenser delta T(condensing temperature minus ambient temperature) now provides morepowerful diagnostic capability of system faults as illustrated belowincluding heat pumps in the heating mode because the delta T becomesevaporation temperature minus ambient temperature. In the chart below inthe cooling mode, the delta T represents condenser delta T and in theheating mode, the delta T represents evaporator delta T. Cooling modHeating mod Outdoor fan blocked/failed Overload trip Low delta T OrOvercharge (High side) High delta T High Tcond High current Indoorblower blocked/failed Low delta T Overload trip Or Loss of Charge (Lowside) Low delta T Low delta T Long run time Long run time Defrostinitiation — High delta T Compressor Fault Current vs. Tcond — Capacityloss % run time % run time

[0078] Finally, it is now possible to diagnose loss of capacity with theaddition of outdoor ambient sensor 334 using percent run time as shownin FIG. 14. Predicting compressor energy use is also now possiblebecause current, voltage and run time are known. The energy usage overtime can be monitored and reported.

[0079] Overall, the implementation of an electronic diagnostic tool isillustrated in FIG. 15 with current sensing devices 102, condensertemperature sensor 332 and outdoor ambient temperature sensor 334. Sincethese sensors provide continuous monitoring of the system and not singleswitches, it is now possible to integrate safety protection capabilityinto this control and eliminate the need for high and low pressuresafety switches.

[0080] Additional diagnostic capabilities can be achieved by sensing thevoltage in the power supply wires powering compressor 10. As shown inFIGS. 2 and 3 illustrate voltage sensors 402 incorporated for thispurpose. Compressors with internal line breaks like temperature sensor54 will “trip” if the supply voltage to compressor 10 falls below aspecified value. This value is typically ten percent below the nominalvoltage. Under this reduced voltage condition, the motor current willincrease to a level that would generate enough heat to “trip” protector54. Hence, if the voltage is known when protector 54 trips, this lowvoltage condition can be flagged as a specific fault. The servicetechnician can then concentrate on finding the cause of the low voltagecondition. The voltage can be sensed by several methods. It may bedirectly sensed at the compressure terminals as shown with sensors 402or at other points in the electrical circuit feeding compressor 10. Itmay also be indirectly sensed by monitoring the control voltage of thesystem using a sensor 404 as shown in FIGS. 2 and 3. The control voltageis typically a low voltage circuit (24 VAC) and it is derived using astep down transformer (not shown). This control voltage would alsochange in direct proportion to the change in line voltage. Hence,monitoring the control voltage could provide an idea of the linevoltage.

[0081] The description of the invention is merely exemplary in natureand, thus, variations that do not depart from the gist of the inventionare intended to be within the scope of the invention. Such variationsare not to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. A diagnostic system for a compressor assemblyincluding a compressor and a motor protector, said system comprisinglogic circuitry associated with the motor protector and operable toanalyze a status of the motor protector as a function of time andidentify a specific fault cause.
 2. The diagnostic system of claim 1,further comprising a demand signal sensor, wherein said logic circuitryis associated with said demand signal sensor.
 3. The diagnostic systemof claim 2, further comprising a current sensor, wherein said logiccircuitry is associated with said current sensor.
 4. The diagnosticsystem according to claim 2, wherein said demand signal sensor monitorsa supply voltage.
 5. The diagnostic system according to claim 2, whereinsaid demand signal sensor is in communication with a system controllersupplying a signal indicating demand.
 6. The diagnostic system accordingto claim 1, further comprising an indicator associated with said logiccircuitry, said indicator receiving a signal from said logic circuitryto indicate a fault based on said current and demand signal.
 7. Thediagnostic system according to claim 6, wherein said indicator is aplurality of lights indicating the presence or absence of a faultcondition.
 8. The diagnostic system according to claim 1, wherein saidlogic circuitry is operable to output a coded sequence of electricalpulses to identify said specific fault cause.
 9. The diagnostic systemaccording to claim 1, wherein said logic circuitry is operable toanalyze said operating condition and identify a specific fault causewhile the compressor is operating.
 10. A method for diagnosing acompressor assembly including a compressor and a motor protector, saidmethod comprising: analyzing a status of the motor protector as afunction of time; and identifying a compressor fault cause based on saidanalyzing.
 11. The method according to claim 10, further comprising:sensing a demand signal; sensing a current; and analyzing said senseddemand signal and said current.
 12. The method according to claim 11,wherein said identifying a compressor fault cause includes indicating aspecific fault cause based on said sensed current and demand signal. 13.The method according to claim 10, wherein said identifying includesoutputting a coded sequence of electrical pulses to identify a specificfault cause.
 14. The method according to claim 10, wherein saididentifying occurs while the compressor is operating.